In conventional optomagnetic recording/reproducing devices, an optical head device opposes one side of an optomagnetic disk, which serves as an information recording medium that is rotated by a driving mechanism. The optical head device emits a light beam for irradiating an optomagnetic recording layer of the optomagnetic disk. A magnetic head device opposes the other side of the optomagnetic disk and applies an external magnetic field to the optomagnetic recording layer.
The optomagnetic recording/reproducing device applies a magnetic field to the optomagnetic recording layer of the rotating optomagnetic disk by letting the magnetic head device modulate the direction of the magnetic field in accordance with the information signal to be recorded, while the optical head emits a light beam that is focused on the optomagnetic recording layer.
This light beam heats a portion of the optomagnetic recording layer to a temperature above the curie temperature, so that this portion loses its coercive force. After this portion has been magnetized in the direction of the magnetic field applied by the magnetic head device, the optomagnetic disk is moved by rotation relative to the light beam, so that the temperature of this portion drops below the curie temperature and the magnetization direction is fixed. Thus, an information signal is recorded in the optomagnetic recording layer.
Since there is a possibility that the optomagnetic disk sways during the rotation, recent optomagnetic recording/reproducing devices comprise sliding magnetic head devices. A sliding magnetic head device records the information signal while sliding on the MD. Such a conventional magnetic head device is disclosed, for example, in Publication of Unexamined Japanese Patent Application No. Hei 8-147914.
The following is a more detailed explanation of a conventional magnetic head device, with reference to FIGS. 9-14. FIG. 9 is a perspective view of an example of a conventional magnetic head device. FIG. 10 is a perspective view of the magnetic head device shown in FIG. 9, taken from the other side. The elastic members 2 are punched from an electrically conductive thin metal sheet of, for example, phosphor bronze or BeCu. The fastening member 3, illustrated in FIGS. 9 and 10, connects the magnetic head device 1 to an optical head device 91 (illustrated in FIG. 13). The fastening member 3 is molded in one piece using a synthetic resin. A slider 5 is molded in one piece from synthetic resin and attached to the front end portion of the pair of elastic members 2. A head-supporting member 6 is molded around the pair of elastic members 2 in one piece using synthetic resin.
FIG. 12 is a side elevation of a system for applying a magnetic field, which is arranged in the slider 5 of FIGS. 9 to 11. A magnetic pole core 32 is E-shaped and formed from magnetic material such as a ferrite. A coil 4 is wound around the central magnetic pole 32a of the magnetic pole core 32. The coil 4 and the magnetic pole core 32 apply a magnetic field, and are fixed to the slider 5. A sliding portion 52 protrudes more towards the optomagnetic disk than the central magnetic pole 32a of the magnetic pole core 32, and slides on the optomagnetic disk.
The sliding portion 52 protrudes from the front end side of the slider 5 opposing the base end side of the elastic members 2. The slider 5 has a second elastically deformable portion 8 of the elastic members 2 in its center. As will be explained further below, when the slider 5 and the head-supporting member 6 are rotated away from the optomagnetic disk 100, the slider 5 abuts a rotation orientation control arm 84. A contacting portion 53 is formed on the front end side of the slider 5 and controls the rotational orientation of the slider 5 relative to the head-supporting member 6. When the slider 5 abuts the rotation orientation control arm 84, it rotates around the second elastically deformable portion 8.
The portion of the pair of elastic members 2 between the fastening member 3 and the head-supporting member 6 is a first elastically deformable portion 7. There is no synthetic resin molded around the first elastically deformable portion 7, so that the elastic members 2 in this portion are exposed. The first elastically deformable portion 7 is the rotation center when the head-supporting member 6 and the slider 5 are rotated forward or away from the optomagnetic disk 100.
Moreover, the portion of the elastic members 2 between the slider 5 and the head-supporting member 6 is the second elastically deformable portion 8. There is no synthetic resin molded around the second elastically deformable portion 8, so that the elastic members 2 in this portion are exposed. The system for applying a magnetic field is attached to the slider 5. The slider 5 follows the swaying of the rotating optomagnetic disk 100, so that the second elastically deformable portion 8 moves elastically back and forth.
The resilience of the first elastically deformable portion 7 and the second elastically deformable portion 8 forces the slider 5 against the optomagnetic disk 100. Thus, the slider 5 slides on the rotating optomagnetic disk 100 with a certain sliding pressure. For the resilient force, a force is sufficient if it causes the slider 5 to glide on the optomagnetic disk 100 with a certain sliding pressure and without separating too much from the surface of the optomagnetic disk 100. When the resilient force is too large, the sliding friction between the slider 5 and the optomagnetic disk 100 increases, and may result in considerable wear of the slider 5 and the optomagnetic disk 100.
Therefore, the resilience and the mechanical strength of the first and the second elastically deformable portions 7 and 8 should be restricted to relative small values. For this reason, the first and the second elastically deformable portions 7 and 8 are formed as plate springs of thin phosphor bronze, for example.
In such a magnetic head device, however, the cantilevered head-supporting member 6 is formed of a thin plate spring with insufficient mechanic strength. Thus, when a shock is applied to the magnetic head device, the load on the cantilevered head-supporting member 6 can easily surpass the elastic limit, so that the head-supporting member 6 is deformed. Especially, when a shock is applied to the head-supporting member 6, the load concentrates on the base end, and the first elastically deformable portion 7 may deform considerably.
This danger of easy deformation as a result of a shock is the same even when the magnetic head device is built into an optomagnetic recording/reproducing device. In this case, if a shock is applied to the optomagnetic recording/reproducing device, the shock is transmitted to the magnetic head device, and the first elastically deformable portion 7 may be deformed easily.
To withstand such shocks, the head-supporting member 6 is provided with a connecting arm 76, as shown in FIGS. 9-11, 13 and 14. This connecting arm 76 is provided at one side of the base end of the head-supporting member 6 near the fastening member 3 and extends in the longitudinal direction of the head-supporting member 6. The connecting arm 76 is provided with a weight 77 on its end.
The weight 77 relocates the center of gravity of the head-supporting member 6, which is supported by the fastening member 3 via the first elastically deformable portion 7, to a spot nearer the first elastically deformable portion 7. In other words, the connection arm 76 extends the head-supporting member 6 beyond the first elastically deformable portion 7 and comprises a weight 77 on its end. The weight 77 is provided on the side of the fastening member 3, with respect to the first elastically deformable portion 7.
A rotation orientation control arm 84 is provided on the end of the side opposite from the connection arm 76, as indicated in FIGS. 9-11, 13, and 14. The rotation orientation control arm 84 is substantially parallel to the head-supporting member 6. The rotation orientation control arm 84 comprises on its end a rotation orientation control portion 85 bent in L-shape, as shown in FIGS. 9 and 10. This rotation orientation control portion 85 opposes the top of the contacting portion 53 protruding at one end of the slider 5.
When the head-supporting member 6 rotates in arrow direction A in FIG. 9 with the first elastically deformable portion 7 at the rotation center, or in other words, when the slider 5 pivoted on the tip of the head-supporting member 6 is rotated away from the sliding surface of the optomagnetic disk 100, the rotation orientation control arm 84 controls the rotational orientation of the slider 5, which rotates around the second elastically deformable portion 8, by abutting the contacting portion 53 with the rotation orientation control portion 85.
Moreover, the fastening member 3 provided at the base end of the pair of elastic members 2 supports the magnetic head device 1 and fixes it to a pedestal 101. The pedestal 101 is movable in such a direction that the slider 5 moves in a radial direction across the optomagnetic disk 100. The pedestal 101 is rigidly connected to the optical head device 91. As is shown in FIG. 10, a hole 79 for inserting a fixing member such as a screw is drilled into the center of the pedestal 101. Moreover, a dowel hole 80 and an dowel concavity 81, which engage with a pair of positioning pins, are drilled into the bottom surface of the fastening member 3. The positioning pins (not shown in the drawings) protrude from the pedestal.
A magnetic head device 1 as described above is connected to a carriage 92, which is arranged movably inside the optomagnetic recording/reproducing device. As shown in FIG. 13, the optical head device 91 is attached to the carriage 92. Thus, the magnetic head device 1 moves in synchronization with the optical head device 91.
A driving mechanism for rotating the disk is attached to a chassis board 93. Also attached to the chassis board 93 is a slide guide axis 94. A through hole 95 for accepting the slide guide axis 94 is drilled into a middle portion of the carriage 92. A pair of upper and lower guide beads 96 and 97 protrude from one end of the carriage 92. The upper and lower guide beads 96 and 97 guide the carriage 92 along a slide guide portion 98 provided on one side of the chassis board 93. Thus, the carriage 92 is supported movably in radial direction of the optomagnetic disk 100, which is contained by a disk cartridge 99, installed inside the optomagnetic recording/reproducing device. The carriage 92 can be moved by a head-feed mechanism that is driven by a motor (not shown in the drawing).
The optical head device 91 is attached to a front end portion of the carriage 92. The objective lens of the optical head device 91 opposes the optomagnetic disk 100 and focuses a light beam emitted from a light source onto the signal recording layer of the optomagnetic disk 100. The optical head device 91 is attached to the carriage 92 in a manner that the optical axis of the objective lens intersects with a line through the center of the optomagnetic disk 100.
The pedestal 101, to which the magnetic head device 1 is attached, is formed on the side of the carriage 92 that is opposite from the side to which the optical head device 91 is attached. The pedestal 101 rises along one side of the disk cartridge 99, which is installed in a cartridge carrying member inside the optomagnetic recording/reproducing device, as illustrated in FIG. 13.
As shown in FIG. 13, the magnetic head device 1 is connected to the carriage 92 by fixing the fastening member 3 to the upper end portion of the pedestal 101, so that the head-supporting member 6 extends over the disk cartridge 99. The magnetic head device 1 is attached to the pedestal 101 by engaging the dowel hole 80 and the dowel concavity 81 provided at the bottom surface of the fastening member 3 with the positioning pins protruding from the upper surface of the pedestal 101 to position the fastening member 3 on the pedestal 101. Then, the fastening member 3 is attached to the pedestal 101 with a screw that is inserted and screwed into the hole 79 to thus insert a fixing member.
The slider 5 is supported by the second elastically deformable portion 8 on the front end of the head-supporting member 6. The central magnetic pole 32a of the magnetic pole core 32 is a part of a system for applying a magnetic field, which is attached to the slider 5. When the magnetic head device 1 is fastened onto the pedestal 101, the central magnetic pole 32a opposes the objective lens of the optical head device 91. The optomagnetic disk 100 is arranged between the central magnetic pole 32a and the objective lens. Thus, an external magnetic field can be applied where a light beam irradiates the optomagnetic disk 100.
The carriage 92 is driven by a head-feeding mechanism. The magnetic head device 1 is moved in the radial direction of the optomagnetic disk 100 (arrow directions B and C in FIG. 14) together with the optical head device 91. The direction in which the magnetic head device 1 moves with respect to the optomagnetic disk 100 is perpendicular to the longitudinal direction of the head-supporting member 6, as indicated in FIG. 14.
However, in conventional magnetic head devices as described above, the weight 77 extends in the longitudinal direction of the magnetic head device 1, so that the magnetic head becomes longer in the longitudinal direction. This stands in the way of miniaturization of the optomagnetic recording/reproducing device.
It is a purpose of the present invention to solve these problems of the prior art and provide a magnetic head device with excellent shock resistance and suitable for miniaturization by substantially aligning the position of a position control member with the center of gravity of a moving member.